Screen Filter Module for Alternating Flow Filtration

ABSTRACT

Improved screen filter modules, related compartmentalized filtration modules, and related filtration processes, suitable for filtering fluid to eliminate suspended particulate matter, such as living cells or microcarriers anchoring living cells, or to separate particulate matter based on size. The improvement is the presence of a barrier that channels redirected filtrate to the portion of the filter most susceptible to clogging by the particulate matter and induces flow patterns that act against clogging.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application61/099,633 filed Sep. 24, 2008 and U.S. provisional application61/099,813 filed Sep. 24, 2009.

FIELD OF THE INVENTION

This invention relates to a device and methods for separating fluid fromparticulate matter such as living cells in suspension or attached to asolid matrix such as “microcarriers,” or nonliving particles suspendedin the fluid.

BACKGROUND OF THE INVENTION

Living cells suspended in fluid growth medium, for example in abioreactor, have been used to generate pharmaceutically usefulmolecules. In many cases, the molecules produced by the cells aredischarged into the growth medium; in other cases, the product is withinthe cells or may constitute the cells themselves; simultaneously, insearch of increased productivity, the practice of cell culture hasevolved. In one culture method, cells are grown in a continuous mannerand to high concentrations by removing waste products from the cultureand replacing with fresh media. In many cases, therefore, separation ofcells from growth medium becomes an essential step in production of cellderived products. Separation of the molecules from the particulate cellsin suspension or attached to microcarriers suspended in the growthmedium can be achieved by a variety of methods. Not excluding othersuspensions or solutions, the focus going forth will be on the use ofanchorage dependent cells cultured on microcarriers. One separationmethod involves a “screen cage” with a mesh of pore size smaller thanthe microcarriers. The cage, in many cases, is placed in the culturevessel itself, and when appropriate, can be used to separatemicrocarriers from suspending medium, retaining the microcarriers withinthe vessel. The screen cage, while used in numerous processes, has anumber of flaws, including that it is prone to clogging. Once clogged,it becomes useless and may result in premature termination of theproduction run at great cost and time loss. Furthermore, the volume ofthe internal screen cage reduces the capacity of the culture productionvessel.

Another method, somewhat like an external screen cage or using a chamberand a partitioning screen, has been used for separation of microcarriersfrom culture medium. It involves continuous pumping of culturesuspension through the screen. The screen retains the microcarriers andthe media flows through. This device results in concentration ofmicrocarriers within the separation chamber; however, while effectivefor short separation steps, it may result in entrapment of themicrocarriers within the screened chamber causing its eventual clogging.Another limitation of this method, inherently results from theconcentration of microcarriers with attached cells within the chamberduring the separation process, a process that can deprive the cells ofessential nutrients and lead to cell damage.

Another method for separating microcarriers from a culture mediuminvolves a settling process, involving the of use of microcarriers, withattached cells, that together are heavier than the suspending medium. Ina static culture, without agitation, the microcarriers, which are ofspecific gravity greater than the suspending medium, will settle to thebottom of the culture vessel, allowing removal of microcarrier-freemedium from the top. While this method is reliable and commonly used, itis not preferred. The settling process is slow and time consuming,particularly at large scale, where settling distances are great. Inaddition, maintaining the cells in an unagitated environment can deprivethe cells of oxygen and other nutrients. The current invention isdesigned to alleviate some of the limitations of other current systems.

The prior art provides filters that allows the molecules, but not largerparticulate matter or cells to pass through it. In order to maximize theproduction of the molecules, systems have been developed to replenishthe medium removed from the suspended entities during the filtrationstep. This has been achieved in the prior art using alternatingtangential flow systems (See U.S. Pat. No. 6,544,424). The systemdescribed in that patent, however, are not well adapted to disposabilitynor does it provide a mechanism for controlling the flow dynamics acrossthe filter surface that may enhance the capacity and efficiency of thefilter. The use of a device that can controls the flow dynamics orpatterns across the filter membrane may be used to enhance theeffectiveness of the filter. The term filter includes, but is notlimited to, any of ultrafiltration filters microfiltration filters,macrofiltration filters as well as screens. The ability to control theflow dynamics across a screen filter facilitates its use, asexemplified, in production of vaccines, a multistep process; examples ofthe steps include an initial wash of microcariers, meaning rapid removalsuspending media through the screen filter and retaining themicrocarries and replenishing removed media with fresh media. Such stepmay be repeated more than once; another step, follows steamsterilization of the suspended microcarriers, which also requires arapid media exchange step, removing sterilization media and replacementwith fresh growth media, so that the subsequent inoculation with cellswill result in rapid attachment and growth of the cells on themicrocarriers; a further step may include removal of growth media fromthe culture, retaining microcarriers and attached cells, followed byaddition of a second, production, media and simultaneously inoculationwith a virus; following viral growth phase, the virus laden cells mayresult in cell lysis; in which case, the screen filter may be used toseparate and harvest the virus, retaining the microcarriers and cellremnants in the culture vessel. Facilitation of such multistep processby an efficient separation device such as described by the invention cangreatly enhance the viral production process and making the process moreefficient, reliable and cost effective. it would be desirable to have aless expensive system, preferably one that could be considereddisposable. A disposable system would not have to be washed or preparedfor use, time consuming efforts that decrease system reliability andincrease operating costs It would also be simpler to dispose of andreplace a spent system by an unused filter module as needed.

The present invention provides an enhanced screen filter module that canbe used in a disposable manner if desired and an enhanced means forcontrolling the flow dynamics across a filter to enhance its filtrationcapacity and its usefulness in a greater range of applications.

BRIEF SUMMARY OF THE INVENTION

In its most general aspect, the invention is an improved screen filtermodule suitable for filtering fluid to separate suspended particulatematter, such as living cells or microcarriers anchoring living cells.The screen module is one adapted for use with an alternating pump thatpulls the fluid through filter and then redirects a portion of thefiltrate back through the filter. The module comprises a chamber withinwhich, for example, particulate matter may be retained. The filterscreen is part of the chamber wall. The improvement is the presence of abarrier that channels the redirected filtrate to the portion of thefilter screen most susceptible to clogging by the particulate matter andgenerates flow dynamics within the filter chamber that inhibits cloggingof the filter screen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a sectional view showing components and compartments of anassembled filtration module of the invention, also showing non-sectionalviews of portions of the assembly. The sectional view of the screenfilter module within the compartmentalized filtration module is takenalong the line 1-1 in FIG. 2.

FIG. 1 b. Enlarged view of the indicated portion of FIG. 1 a.

FIG. 2 is a side view of a screen filter module of the invention, whichmodule is shown in section as part of a.

FIG. 3 is a sectional view of the screen filter module shown in FIG. 2,taken along the line 3-3 in FIG. 2.

FIG. 4 is a side view of a screen filter module of the invention, whichmodule employs a pleated screen filter.

FIG. 5 is a top view of the module shown in FIG. 4.

FIG. 6 is a 4× enlarged view of the indicated portion of FIG. 7.

FIG. 7 is a sectional view of the screen filter module shown in FIGS. 4and 5, the view taken along the line 7-7 in FIG. 5.

FIG. 8 is a sectional via of the screen filter module shown in FIG. 4,taken along the line 8-8 in FIG. 4.

FIG. 9 is a sectional view of the screen filter module shown in FIG. 4,taken along the line 9-9 in FIG. 4.

FIG. 10 is a partial sectional view of a compartmentalized filtrationmodule of the invention.

FIGS. 11 a and 11 b are versions of FIG. 10 in which arrows describeflow patterns if fluid is present in the compartmentalized filtrationmodule. FIGS. 11 a and 11 b show the flow patterns in oppositedirections, depending on the force exerted by the alternating pump usedin the compartmentalized filtration module.

FIG. 11 c is an enlarged view of the indicated portion of FIG. 11 a.

FIG. 11 d is an enlarged view of the indicated portion of FIG. 11 b.

FIG. 12. Isometric view of the screen filter module shown in FIG. 10.

FIG. 13. Sectional view of the screen filter module shown in FIG. 12.

FIG. 14. Sectional view of a compartmentalized filtration module of theinvention, also showing a non-sectional views a portion of the module,the views being center isometric, the module an example of one where theflow barrier is internal to the retentate chamber.

FIG. 15. Sectional view of the compartmentalized filtration module ofthe invention shown in section in FIG. 14 wherein the sectional view isalong the line 15-15 in FIG. 14, but for the entire module, not just theportion of the module shown in cross section in FIG. 14.

FIG. 16. Variation of invention shown in FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

The invention has six general aspects:

In a first aspect, the invention is a screen filter module enhanced withan external barrier, the module comprising:

a) a retentate chamber, said chamber comprising a chamber wall and achamber entrance, said chamber entrance permitting fluid containingsuspended particulate matter (for example, fluid from a bioreactor) toenter or exit the chamber, and wherein the chamber wall comprises afilter screen, said screen comprising pores, such that said screenpermits fluid and particles smaller than the pores but not suspendedparticulate matter larger than the pores to flow through it;

b) a barrier, said barrier positioned exterior to the retentate chamberso as to redirect fluid moving through the filter screen area proximalto the chamber entrance so that the redirected fluid moves towards afilter screen area more distal to the chamber entrance;

c) an exiting space between the filter screen and the barrier, saidspace for permitting fluid flow;

d) an opening between the filter screen and the perimeter of thebarrier, said opening providing a means for fluid to leave the exitingspace and escape the module; and

e) an upper adapter for attachment to the (preferably tubular) filterscreen (preferably at the upper end of said screen when said screen withits main axis vertically disposed), said adapter also attached to arigid portion of the screen filter module, so as to prevent collapse ofthe filter screen.

In the first aspect of the invention, it is optional and preferable thatthe filter screen module further comprise a base adapter for attachingthe barrier to the retentate chamber and/or anchoring the filter screenwhen used in a compartmentalized filtration module.

In a second aspect, the invention is a screen filter module enhancedwith an internal barrier, the module comprising:

a) a filtrate chamber, said chamber comprising a chamber wall and achamber entrance, said chamber entrance permitting fluid to exit orenter the chamber, and wherein the chamber wall comprises a filterscreen, said screen comprising pores, such that said screen permitsfluid and particles smaller than the pores but not suspended particulatematter that is larger than the pores, to flow through it;

b) a barrier, said barrier positioned inside the filtrate chamber so asto redirect filtrate chamber fluid moving towards a filter screen areadistal to the filtrate chamber entrance so that the redirected fluidmoves within the filtrate chamber towards a filter screen area moreproximal to the filtrate chamber entrance and exits the filtrate chamberso as to flow into the retentate chamber;

c) an opening in said barrier to allow limited fluid flow through thebarrier;

d) a bypass space between said barrier and the filtrate chamber wall,said space for permitting fluid entering the filtrate chamber throughthe filter screen to bypass the barrier and flow to the filtrate chamberexit; and

e) a lower adapter attached to the filter screen.

In the second aspect of the invention, it is optional and preferablethat the filter screen module further comprise a base adapter forattaching the barrier to the filtrate chamber and/or anchoring thescreen filter module when used in a compartmentalized filtration module.

In a third aspect, the invention is a compartmentalized filtrationmodule (also referred to herein simply as a “filtration module”) thatcontains a screen module enhanced with an external barrier such that thescreen filter module comprises a retentate chamber, the filtrationmodule comprising:

a) a retentate chamber, said retentate chamber comprising a retentatechamber wall and a retentate chamber entrance, said entrance permittingfluid containing suspended particulate matter to enter and exit thechamber, said retentate chamber wall comprising a filter screen, saidscreen comprising pores, such that said that said screen permits fluidand particles smaller than said pores but not suspended particulatematter larger than the pores to flow through it;

b) a filtrate chamber adjoining said retentate chamber, said filtratechamber comprising a filtrate chamber wall and a filtrate chamberentrance, said filtrate chamber wall comprising the filter screen alsocomprised by the retentate chamber wall, said filtrate chamber entrancepermitting fluid to enter or exit the filtrate chamber;

c) an alternating pump connected to the filtrate chamber entrance, saidpump for pumping fluid in alternating directions through the filtratechamber entrance and thereby for pumping fluid in alternating directionsthrough the filter screen;

d) a barrier, said barrier positioned inside the filtrate chamber so asto redirect fluid moving through the filter screen area proximal to theretentate chamber entrance so that the redirected fluid moves towards afilter screen area more distal to the retentate chamber entrance;

e) an exiting space between the filter screen and the barrier, saidspace for permitting fluid flow;

f) an opening between the filter screen and the perimeter of thebarrier, said opening providing a means for fluid to escape the exitingspace and the retentate chamber;

g) an upper adapter for attachment to the (preferably tubular) filterscreen (preferably at the upper end of said screen when said screen withits main axis vertically disposed), said adapter also attached to arigid portion of the screen filter module, so as to prevent collapse ofthe filter screen; and

h) a harvest port for removing fluid from the filtrate chamber.

In the third aspect of the invention, it is optional and preferable thatthe filter screen module further comprise a base adapter for attachingthe barrier and/or anchoring the filter screen module in thecompartmentalized filtration module.

In a fourth aspect, the invention is a compartmentalized filtrationmodule that contains a screen filter module enhanced with an internalbarrier such that the screen filter module functions as the filtratechamber, the filtration module comprising:

a) a retentate chamber, said retentate chamber comprising a retentatechamber wall and a retentate chamber entrance, said entrance permittingfluid containing suspended particulate matter to enter and exit thechamber, said retentate chamber wall comprising a filter screen, saidscreen comprising pores such that said screen permits fluid andparticles smaller than said pores but not suspended particulate matterlarger than said pores to flow through it;

b) a filtrate chamber adjoining said retentate chamber, said filtratechamber comprising a filtrate chamber wall and a filtrate chamberentrance, said filtrate chamber wall comprising the filter screen alsocomprised by the retentate chamber wall, said filtrate chamber entrancepermitting fluid to enter or exit the filtrate chamber;

c) an alternating pump connected to the filtrate chamber entrance, saidpump for pumping fluid in alternating directions through the filtratechamber entrance and thereby for pumping fluid in alternating directionsthrough the filter screen;

d) a barrier, said barrier positioned inside the filtrate chamber forredirecting fluid moving towards a filter screen area distal to thefiltrate chamber entrance so that said redirected fluid moves throughthe filter screen area more proximal to the filtrate chamber entrance;

e) a bypass space between said barrier and the filtrate chamber wall,said space for permitting fluid entering the filtrate chamber throughthe filter screen to bypass the barrier and flow to the filtrate chamberentrance;

f) an opening in said barrier to allow limited fluid flow through thebarrier;

g) a lower adapter for attachment to the filter screen, said adapteralso attached to a rigid portion of the filtration module, so as toprevent movement of the filter screen; and

h) a harvest port connected to said alternating pump, said port forremoving fluid pumped from the filtrate chamber,

In the fourth aspect of the invention, it is optional and preferablethat the compartmentalized filtration module further comprise a baseadapter for attaching the barrier to the filtrate chamber and/oranchoring the screen filter module in the compartmentalized filtrationmodule.

In a fifth aspect, the invention is a process for removing particulatematter from a fluid in which it is suspended, the process being anexample of one that utilizes the screen filter module enhanced with anexternal barrier, the process comprising the steps of:

a) feeding a suspension into a retentate chamber via an entrance in thatchamber, said entrance being the retentate chamber entrance, saidsuspension comprising the particulate matter suspended in the fluid,said retentate chamber connected to a filtrate chamber via a sharedfilter screen in their respective walls, said filter screen comprisingpores of a size that allow the fluid and particles smaller than thescreen pores but not the suspended particulate matter that are largerthan the screen pores to pass through, said filtrate chamber comprisingan entrance connected to an alternating pump;

b) directing the suspension at the filter screen so that fluid but notsaid suspended particulate matter passes through the filter screen, saiddirecting achieved by the action of the alternating pump;

c) collecting, in the filtrate chamber, the fluid that passed throughthe screen filter, said collected fluid being the filtrate fluid;

d) removing a portion of the filtrate fluid from the filtrate chamber,thereby leaving unremoved filtrate fluid in the filtrate chamber;

e) directing the unremoved filtrate fluid back at the screen filter,such filter screen directing achieved by the alternating pump exerting aforce on said unremoved filtrate fluid, such that a barrier redirectsfiltrate fluid moving towards a filter screen area proximal to theretentate chamber entrance so that the redirected fluid moves towards ascreen filter area more distal to the retentate chamber entrance; and

f) repeating steps (a) through (e).

In a sixth aspect, the invention is a process for removing particulatematter from a fluid in which it is suspended, the process being anexample of one that utilizes the screen filter module enhanced with aninternal barrier, the process comprising the steps of:

a) feeding a suspension into a retentate chamber via an entrance in thatchamber, said entrance being the retentate chamber entrance, saidsuspension comprising the particulate matter suspended in the fluid,said retentate chamber connected to a filtrate chamber via a sharedfilter screen in their respective walls, said filter screen comprisingpores, said pores of a size that allow the fluid and particles smallerthan the pores but not the suspended particulate matter that are largerthan the screen pores to pass through, said filtrate chamber comprisingan entrance connected to an alternating pump;

b) directing the suspension at the screen so that fluid but not saidsuspended particulate matter passes through the filter screen, saiddirecting achieved by the action of the alternating pump;

c) collecting, in the filtrate chamber, the fluid that passed throughthe filter screen, said collected fluid being the filtrate fluid;

d) removing a portion of the filtrate fluid from the filtrate chamber,thereby leaving unremoved filtrate fluid in the filtrate chamber;

e) directing the unremoved filtrate fluid back at the screen filter,such directing achieved by the alternating pump exerting a force on saidunremoved filtrate fluid, such that a barrier redirects fluid movingtowards a screen filter area distal to the filtrate chamber entrance sothat the redirected fluid moves towards a screen filter area moreproximal to the filtrate chamber exit; and

f) Repeating steps (a) through (e).

In the sixth aspect of the invention, a portion of the fluid (preferablyless than 50 percent, more preferably less than a third) is permitted toflow through the barrier which may have small openings.

As can be seen from the modules exemplified in the drawings, it ispreferable that the filter screen be elongated in the direction of itsmain axis and be symmetrical as possible around that axis.

The materials used to make the filter screen module and thecompartmentalized two-chamber module are preferably synthetic polymersor plastics so as to reduce material and production cost relative to ametal construction and make it more economical to treat it as adisposable module. Preferred plastic for the filter module body arepolysulfone, polycarbonate, kynar and others, and for the base adapter,barrier, and upper adapter they are: polysulfone, polycarbonate, kynarand others, and the screen material they are: polyester, PVDF, Kevlarand others; preferably such plastics are high performance capable ofwithstanding steam sterilization or sterilization by other means.

The filter screen is preferably made of pores separated by the minimalamount of plastic required for structural integrity and stability. Thefilter screen will most likely correspond to a foldable, collapsiblemesh whose collapse is prevented in the module because of the rigidsupport provided by other portions of the module to which the mesh isadhered to.

Pore sizes capable of preventing passage of living animal cells ormicrocarriers generally range, respectively, from 0.1 micron to 80microns. Spherical microcarriers typically have a diameter in the range100 to 500 microns, so the pore size will have to be less than themicrocarrier diameter used. The pores normally required in such case isabout 75 micron in order to allow desired molecules, present in thefluid, to pass through the filter but not the larger microcarriers.Examples of desired molecules are antibodies, viruses, and otherpharmaceutically active molecules. The minimum size will depend on thatneeded to allow the molecules to pass through the filters. The moleculeswill be those that were produced by the living cells, and thereforenormally be smaller than the cells or microcarriers.

The pore size can also be chosen to allow particles of a larger size tobe separated from particles of a smaller size.

The screen filter module is preferably used with aqueous fluids, usuallyenhanced with regard to pH, salts and nutrients as needed for livingcells.

Sterilization of the screen filter module prior to use can be achievedby autoclaving or other forms of steam sterilization or sterilization byradiation or by chemical means. Sterilization of the compartmentalizedfilter module can be achieved by similar means. When using plasticmaterials, the components can, where necessary, be caused to adhere toeach other using adhesives such as high temperature epoxies,cyanoacrylates, heat, mechanical coupling, ultrasonic welding, orsolvents. The surface area of the filter screen is based on applicationand volume of culture to be processes, and is preferably in the rangebetween 10 and 10,000 cm². The length, diameter and configuration of thescreen are not limited but may vary considerably based on application.

The filter screen may be tapered, so that, in the first aspect of theinvention, for example, its attachment diameter at the point it meetsthe module's upper adapter is smaller than the attachment diameter whereit meets to the lower scaffold perimeter.

When the module is part of a compartmentalized filter module of thisinvention, the entrances of the two chambers and the alternating pumpare preferably aligned along the main axis of symmetry of the screenfilter module.

When the barrier is external to the filter screen, it preferablyredirects fluid away from portion of the filter that extends from thefilter entrance almost the entire length of the filter (preferably atleast 50 percent (more preferably at least 70 percent) of the entirelength, preferably not more than 99 percent of the entire length)towards where it meets the upper adapter.

The scaffold element is a structural component that is added to preventcollapse of the filter screen and/or its movement when subjected tofluid moving under pressure. For screen filter modules which areintended to be used while vertically disposed with the retentate chamberentrance at the lower end, the upper end of the filter screen (alongwith the attached upper adapter) would collapse under the force ofgravity or stress created by the alternating flow, absent a scaffoldelement. The scaffold element in that case is preferably linked to theportion of the filter screen most distal to the chamber entrance (i.e.,the higher end of the filter screen) to the surrounding barrier. Thescaffold element may be attached directly to the filter screen or,preferably, indirectly by virtue of being attached to the upper adapterwhich in turn is attached to the filter screen. The scaffold element maybe an extension of the barrier, and to some extent will therefore affectfluid flow but that is not its primary function.

When the barrier is internal to the screen filter as in the second,fourth and sixth aspects of the invention, the screen filter module maybe attached at its entrance end to the outer perimeter of the pump fluidchamber outlet. The other end of the module may be attached to a loweradapter. The lower adapter in turn is fixed within the filtration moduleby its attachment to the filtration module wall with a high strengthbridge or link, preferably wire or thread that will not interfere withmovement of retentate within the filtration module chamber.

In addition to the advantages described above for the current invention,the invention is designed to allow or perform rapid separation steps ofmicrocarriers or other particles from their suspending medium, asrequired in some production processes. It is also designed to allowrapid and continuous reversible flow of cells growing attached to themicrocarriers between the culture vessel and filtration modulesresulting in removal of cells from the culture vessel for only a shorttime, followed by the rapid return of the cells to the culture vesselwhere the cells are nourished. The reversible flow allows rapidequilibration of the content in the culture vessel with the culture inthe filtration module, keeping the cells nourished and in good conditionduring the filtration process. As there may be several filtration stepsduring a production process, which may include several manipulations ofthe cultured cells, it is essential that the cells be maintained inoptimally viable conditions during the filtration steps. Damaging theculture during any of the steps may be detrimental to the remainder ofthe production process.

The inventions may be further understood by reference to the attachedFigures.

FIG. 10 illustrates a compartmentalized filtration module 401 thatcomprises a screen filter module 405. The compartmentalized filtrationmodule 401 is an example of the third aspect of the invention and thescreen filter module 405 is an example of the first aspect of theinvention.

FIG. 12 shows a center isometric view of the screen module 405 of FIG.10. FIG. 13 shows a fully cross-sectional view of the screen module 405.FIG. 12 and FIG. 13 together show that the screen filter module 405 isan example of the first aspect of the invention. The module comprises aretentate chamber 445, a chamber wall 460, a chamber entrance 443, and afilter screen 417 that is part of the chamber wall. The chamber wall 460comprises the screen filter 417 and a surface 534 of the upper adapter441. The module also comprises a barrier 419 exterior to the chamber 445and further comprises an exiting space 464 between the screen filter 417and the barrier 419. The screen filter 417 adheres to upper adapter 441by mechanical means (FIG. 10) via an adhesive layer 526 (FIG. 12; seealso FIGS. 4, 6, 7 and 13) or by other means. The upper adapter 441 isattached to the barrier 419 be means of fasteners, other mechanicalmeans, heat, ultrasonic welding or adhesives; shown is attachment with aglue layer 527 and barrier adapter posts 449 that are part of thebarrier 419 and that fit into the scaffold post receptacles (as shownfor receptacles 300 in FIG. 6) that are part of the upper adapter 441.At the other end of the module, the screen and barrier are attached tothe screen filter module base adapter 440, (“also referred to as the“lower screen adapter”) the screen 417 by adhesive layer 448, althoughother means of attachment are possible. Together, the upper adapter 441,the base adapter 440, the barrier 419, and barrier adapter posts 449provide support for the screen filter 417, allowing it to be firmlystretched between the adapters 440 and 441. The screen thus fixed atboth ends to respective adapters 440 and 441 is firmly positioned,preventing its collapse during the stresses of the filtration process.The width of posts 449 is selected to optimize flow between retentateand filtrate chambers. Also considered in selecting the width of theposts is their indicated use as means of attaching adapter 441 with theattached screen 417 to the barrier body, where the width affects theflexibility of the post. Attachment of the post 449 to upper adapter 441with a slight inward, (towards the center axis of the module), bend ortension so as to force the attached adapter 441 upward; thereby pulingthe attached screen 417 upward, maintaining it taught. The overcut 222(lower portion of post 249), shown in FIG. 4, is designed to addflexibility to the post and to increase the range of bending.

In FIG. 13, the majority of the fluid directed at the area 522 of thescreen proximal to the retentate chamber entrance 443 will be redirectedto the area 520 of the filter screen that is more distal to theretentate chamber entrance 443.

In FIGS. 12 and 13, it can further be seen that, between the filterscreen 417 and the inner perimeter the restrictive platform 420, (andtherefore effectively between the filter screen 417 and the barrier 419)there is an opening 540. The presence of the restrictive platform 420,which is part of the barrier 419, directs fluid, flowing from the pumpexit end 478 (See FIG. 10) into the filtrate compartment 410(“compartment” and “chamber” are used interchangeably herein), into theretentate compartment 445, through the upper area 418 of the screen 417and restricts the fluid flow that otherwise would go into exiting space464 between the screen 417 and the barrier 419, areas of the screen thatare more proximal to the retentate entrance opening 443.

The filter screen 417 will be porous, so as to allow fluid and particlessmaller than the screen pores to pass through it. However, pores of thefilter will be sufficiently small to retain and prevent suspendedparticulate matter larger than the screen pores to leave the chamber445.

FIG. 10 shows a view of the compartmentalized filtration module 401 thatcomprises a screen filter module 405. FIG. 10 is a center isometricsectional view except for part of the screen filter module 405. Thescreen filter module 405 is shown in a partially sectional isometricview that can be further understood from FIGS. 11 a, 11 b, 12 and 13.The compartmentalized filtration module 401 is essentially symmetricalaround its longitudinal axis. (The harvest port 412 is, however, shownwhile only at one position is not limited to its length orconfiguration, nor are the numbers and positions of the post limited;preferably, harvest port opening 424 is positioned above the screen,such that when harvesting from the harvest port, removing air from thesystem and displacing it with liquid from the culture vessel flowinginto the filtration module through the screen, thus immersing the screenin liquid and assuring full flow across the exit end 442 and upperscreen area 418, between retentate and filtrate compartments, 445 and410, respectively).

In FIG. 10, the compartmentalized filtration module 401 comprises notonly the screen filter module 405, but also a filtrate chamber 410. Thefiltrate chamber is enclosed by a filtrate chamber wall 504 thatcomprises the outer filtrate chamber wall 415 the base adapter plate 416the filter screen 417 and an upper wall formed by the pump housing 404,and specifically its external wall 433. Accordingly, the filter screen417 is part of both the filtrate chamber wall 504 and the retentatechamber wall 460 (See FIG. 13).

FIG. 10 also shows the alternating pump 404 which is connected to thefiltrate chamber entrance 478 which, depending on the direction of fluidflow, can also function as the filtrate chamber exit. Here chamberentrance/exit 478 is also the pump opening through which fluid isexchanged between the pump and the filtrate chamber. The pump 404comprises a fluid pump chamber 407, an air pump chamber 408, and adiaphragm 406 separating the fluid pump chamber 407 and the air pumpchamber 408. An air inlet assembly 421 that alternately directscompressed air into chamber 408 or exhausts that chamber is also shownconnected to the pump 404.

Further evident in FIG. 10 is a base adapter 510 which comprises anadapter plate 416 and a conical adapter 462. The conical nature of theadapter inhibits settling of microcarriers on the adapter surface andfacilitates their flow towards the fluid connector 403 through whichfluid can flow from the retentate chamber entrance 443 to the culturevessel followed by flow from the culture vessel in the reversedirection.

In FIG. 10 the alternating pump 404 is connected directly to thefiltrate chamber 410. In a variation of the aspect of the inventionillustrated in FIG. 10, the alternating pump is connected to thefiltrate chamber by an intervening conduit 499 as shown in FIG. 16.

Fluid flow across the filter screen 417 can be initially primed byactivation of harvest pump 414 and removing air, through lines 412 and413, from the filtration module 401, replacing air with liquid, flowinginto the filtration module 401 through fluid connector 403, which isconnected at its other end to the culture container (not shown). Fillingretentate chamber 445 with unfiltered retentate fluid, followed by flowinto the filtrate chamber 410 into across screen 417, filling bothchambers and immersing barrier and screen in fluid so there is fluidcontact between the chambers. Pressure on either the fluid within thechamber 445 or the fluid exterior to the chamber can be exerted by analternating pump to move fluid through the filter screen. But the poresof the filter will be sufficiently small to prevent the suspendedparticulate matter larger than the screen pores to leave the chamber445, these capabilities in combination with harvesting liquid andparticles smaller than the screen pores can be used to isolate smallmolecules that pass through the filter with the fluid or alternatively,by elimination of fluid from the chamber 445, to isolate the particulatematter in more concentrated form.

The restrictive platform 420, the screen exit end 442, and the barrieradapter posts 449, can be understood by reference to FIGS. 12 and 13 andthe related descriptions.

FIGS. 11 a and 11 b show the same compartmentalized filtration module401 as is shown in FIG. 10, but shows how the direction of fluid flow ischanged by the action of the pump 404.

In FIG. 11 a, flow line arrows 470 shows air flow direction into thepump chamber 408, pressurizing that chamber and forcing diaphragm 406 toexpand into chamber 407, forcing fluid from that chamber. Flow lines,471, 473 and 474 illustrate one flow pattern for fluid directed by thepump 404 from the filtrate chamber 410 at the filter screen 417 isforced to flow to a filter screen exit end 442 (corresponding also toupper screen area 418), which exit end is distal to the retentatechamber entrance 443. Flow thus generated will dislodge microcarriers orparticulates attached to the corresponding, retentate chamber wall orinner screen wall 417. The microcarriers thus dislodges will be dilutedby the inflow of filtrate and forced to flow from the exit end 442towards the entrance end 443 and back to the main culture via the fluidconnector 403. Absent the barrier 419, the fluid emerging from pump 404will flow from the filtrate side into the retentate side across thescreen uncontrolled or directed. The flow across the screen may occuranywhere along the screen including predominantly at its base adjacentto the entrance 443, which may in fact be the path of least resistance.Such flow would result in retaining microcarriers at increasedconcentration towards the distal end of the filter. Subsequent cycles ofthe pump and continued return of filtrate at the proximal end of thefilter, at the entrance 443 side will further accumulate microcarriersat the distal end, which may eventually clog the screen. Continuedremoval of filtrate from the filtrate chamber 410 will add to the aboveindicated concentrating effect on the microcarriers.

In FIG. 11 b, flow line arrows 480 shows the exhaust of pump chamber 408forcing diaphragm to move into the exhausted space of that chamber andinversely causing pump chamber 407 to expand and fill with the filtratefluid. Arrows 481, 484, 485, and 487 illustrate a second flow patternfor fluid directed by the pump 404 in a direction from the retentatechamber entrance 443, into the retentate chamber 445, through the filterscreen 417 through filter exit end 442 and upper screen area 418, intofiltrate chamber 410. The flow is completed by pump 404 return of thefiltrate into pump chamber 407. Noting the flow in this direction,towards the pump, it is preferable to have the flux of fluid flow fromthe retentate chamber to the filtrate chamber more uniformly distributedacross the entire surface of the screen so as to minimize localizedconcentration of microcarriers within the filter module. Morepreferable, is that any concentration of microcarriers occur proximal tothe entrance end 443 of the filter, to facilitate the return ofmicrocarriers to the main culture vessel through fluid connector 403.

To facilitate objectives described in the above paragraph, secondarybarrier openings 476 and a one directional check valves 477 are used. Inthe flow shown in FIG. 11 b, check valve 477 permit a fraction of thetotal fluid flow across screen 417 (see enlarged view FIG. 11 d) throughbarrier opening 476 from the proximal region to the entrance end 443 ofthe filter into filtrate compartment 410; thereby, reducing theconcentrating microcarriers at filter distal end. Flow across the screeninto exiting space 464 facilitates this process. (This is furtheremphasized in FIG. 1 a, by use of a constrictive “O” ring 30 around thescreen 17 to permit greater unrestricted flow from the proximal end(proximal to entrance 43) of the retenate compartment to the filtratecompartment and through space 64.) On the reverse flow shown in FIG. 11a, check valve 477 blocks flow through openings 476, forcing the flowfrom the filtrate compartment to the retentate compartment through upperscreen area 418 and adjacent screen region. These secondary barrieropenings are optional and the degree of flow they allow when presentdoes not change the fact that in FIG. 11, the majority of the fluiddirected at the area 522 of the filter screen proximal to the retentatechamber entrance 443 will be redirected to an area 520 of the filterscreen that is more distal to the retentate chamber entrance 443.

Also evident in FIGS. 11 a and 11 b are the filtrate chamber 410, andthe retentate chamber 445. Fluid flows from the retentate chamber intothe filtrate chamber and then via the harvest port 412, harvest pump414, and harvest line 413 for collection and/or further processing.

FIGS. 4 through 9 together show a pleated version of a screen filtermodule 205 that is an example of the first aspect of the invention. FIG.4 is a side view except that part of that view, at the lower left, showsa side view with a portion of the barrier 219 absent. Without thebarrier, the filter screen 217, the adhesive layer 248, and lower screenadapter (also a base adapter) 240 are visible.

FIG. 4 shows a view of a version of the screen filter module 205 thatcontains a step 252 that is part of the lower screen adapter 240. Asimilar step 52 that is part of the lower screen adapter 40 is shown inFIGS. 1 and 2; its insertion into a counterpart receptacle 57facilitates positioning and securing the screen filter module in acompartmentalized filter module (such as in FIG. 1 where the step 52facilitates insertion into a receptacle (socket) defined by the outerfiltrate chamber wall 15 and the base adapter 110.) An O-ring 251 (51 inFIGS. 1 and 2) that encircles the lower screen adapter 240 (40 in FIGS.1 and 2) seals the lower screen adapter against the filter housing thuseffectively preventing leakage of retentate into the filtratecompartment.

The pleated version of the screen filter module 205 shown in FIGS. 4through 9 can be used the same as the screen filter modules shown inFIGS. 1 a, 1 b, and 10 through 13 and used in the compartmentalizedfiltration module 401 in a manner shown in FIGS. 1, 10 and 11. The lowerscreen adapter 240 and the O-ring 251, shown in FIGS. 4 and 7, can befitted into a housing similar to 415 in FIG. 10 to form a fluid tightseal. The actual screen module shown in FIG. 10 is, however, secured tobase 510. Cross-sectional views FIGS. 8 and 9 show where the filterscreen 217 has been gathered to form four pleats 246. How the pleats 246increase in size as one proceeds from the base to the top of the filterscreen module is show not only by comparing FIG. 8 to FIG. 9, but byviewing FIG. 7. While four pleats are shown, it is obvious that more orless pleats can be used, the depth of the pleats varies as well as theirconfiguration.

Evident in the module illustrated in FIGS. 4 through 9 are the barrieradapter post 249 also referred to as a scaffold element), the upperadapter 241 (also referred to as the scaffold adapter), the pleats 246,the barrier 219 and the perimeter 227 of the barrier 219. The scaffoldadapter 241 is attached to the barrier 219 by means of barrier adapterposts 249 that are part of the barrier itself, where the posts fit intoand are pinned or glued 327 to the scaffold post receptacles 300 thatare part of the scaffold adapter 241. Together, the upper adapter 241and the barrier 219 provide support for the filter screen 217,preventing its collapse during the filtration process.

Also evident in the module illustrated in FIGS. 4 through 9 are theretentate chamber 245, upper screen area 218, exiting space 264,retentate chamber entrance 243, and retentate chamber wall 260. Thechamber wall 260 comprises the filter screen 217 and a lower surface 334of the upper adapter 241 and inner surface of lower screen adapter 240.In FIG. 4 adhesion layer 326, attaching the screen to the upper adapter241, and adhesion layer 248, attaching screen 217 to lower screenadapter 240, are shown.

FIGS. 1 a, 1 b, 2 and 3 together show another example of a reusablescreen filter module 5 that is a first aspect of the invention as wellas a compartmentalized filtration module 1 that utilizes filter module5. FIG. 1 a shows a filtration module that can be assembled ordisassembled, noting the reversible “S” line sanitary connections, ascommon in the industry. Also shown are: fluid connector 3, alternatingpump 4, 6, fluid chamber 7, air pump chamber 8, harvest line 13, andsanitary connections and clamp 39 between parts; noting further, thesanitary gasket 25 used in such connections, including two adjacentflanges 37 and 38 and a clamp 39 to seal the flanges against the gasketto secure the seal. FIG. 1 a also shows filtrate chamber 10, an, outerfiltrate chamber wall 15, barrier 19, perimeter 27 of the barrier 19,filter screen 17, upper area 18 of the screen, air inlet adapter 21,exit end 42, retentate chamber entrance 43, retentate chamber 45, O-ring51, step 52, surface 34 of the upper adapter 41, the retentate chamberwall 60, exiting space 64, filtrate chamber entrance 78 (which overlapswith fluid chamber 7 and is not limited to the size shown) and the baseadapter 110, area 120 of the filter screen that is more distal to theretentate chamber entrance 43, and area 122 of the screen proximal tothe retentate chamber entrance 43, opening 140 between the barrierperimeter 27 and the screen 17, filtrate chamber wall 104 and theharvest port 12.

Also shown in FIGS. 1 a, 1 b, 2 and/or 3 are a center post 128 that isconnected to and supports the upper and lower screen adapters, 41 and40, respectively, where ledge 58 in post 128 upholds adapter 41 fromsliding down and a pin or set screw 53 secures post 128 to the lowerscreen adapter 40. Opening 54 in adapter wall 40 provides access to theset screw with a wrench or a tool for maneuvering the screw or pin 53into opening 55 and forcing the screw against post 128 to secure itsposition against the lower adapter 40. Noting “O” ring 26, to which oneend of the screen is mechanically attached, by sewing or other means,The “O” ring, in turn is mechanically secured against the base adapter40, also by common means; similar attachment of an “O” ring to thesecond end of the screen and their attachment to the upper adapter 41 isachieved; thereby, having the ability to slide adapter 40 against post128 and securing the two adapters with screw 53 allows extension of thescreen 17 between the two adapters and keeping it taught. Also shown isa pressure meter 130 to monitor pressure changed within the filtrationmodule. Other instruments may be added by those skilled in the art tomonitor various parameters within the filtration module; an air inletassembly 32 containing a sterilizing air filter and the means forattaching to air inlet port 21. The double arrow 23 illustrates the twodirections for air flow to and from pump chamber 8, resulting in pumpaction.

FIGS. 14 and 15 together demonstrate another variation of the screenfilter module 605 and the compartmentalized filtration module 601. Thevariations are the second and fourth aspects of the invention (used forthe sixth aspect), respectively. While variation in FIG. 14 shows asectional view of a compartmentalized filtration module of theinvention, it also shows non-sectional views of a portion of the module,the views being center isometric. In these variations, the module is anexample of one where the flow barrier 619 is internal to the filtratechamber 610. FIG. 15 is a sectional view of the compartmentalizedfiltration module of the invention shown in section in FIG. 14. (In FIG.15, the circular ring for the filter screen 617 is represented by asolid line but in fact represents a cross section of the filter screen617). The filtrate chamber 610 is inside the screen 617 and theretentate chamber 645 is external to the screen; noting also that thebarrier 619 is within the inner perimeter of the screen 617 and unlikethe previous examples the screen filter module 605 is inverted andimmersed in retentate. notwithstanding those differences, the twoversions are similar in most other respects; both, filtrate andretentate chamber share a common screen wall 660; pump 604 which pumpsfiltrate reversibly into the filtrate chamber 610 which flows reversiblyacross the screen 617 into the retentate chamber, which retantate flowsreversibly between said chamber and culture vessel through connectingconduit 603; noting other similar features: barrier 619, now locatedwithin the screen 617 and within the screen filter module 605, has asimilar functions to previously ascribed to the external barrier; theirfunction remains largely to direct fluid flow across the screen 617;platform 746, which again directs filtrate flow from the filtratechamber 610 to the retentate chamber 645, preferably, at its more distalend from retentate chamber entrance 643, dislodging microcarriersattached to the retentate screen wall 660 and facilitating their returnto the culture vessel as before; further, openings 732 whose size andconfiguration may used to control the extent of filtrate flow betweenthe distal and proximal segments, (relative to the retentate entrance643), of the filtrate chamber 610, thereby, controlling the extent offlow across different segments of the screen. Addition of air to pumpchamber 608, as previously described, generates flow from the filtratechamber to the retentate chamber, towards the culture vessel; one suchflow direction is shown by lines 671. Exhausting chamber 608 reversesthe flow direction as previously described. Means for removal offiltered harvest through the harvest port 612 is shown. The loweradapter 641 is the counterpart of upper adapters 41, 241 or 441 when itis used in FIGS. 1 through 13. Specific to FIGS. 14 and 15 are the upperbarrier surface 746, the wires 736 which function as a stabilizingelements for the screen filter module by virtue of their attachment tobase adapter 710.

Also shown in FIGS. 14 and/or 15 are fluid connector 603, alternatingpump 604, fluid chamber 607, harvest port 612, outer filtrate chamberwall 615, upper area 618 of the screen, screen filter exit end 642,retentate chamber entrance 643, retentate chamber 645, glue adhesivelayer 648, flow lines 671, adhesive layer 726, center post 731, andsmall openings 732 (four are shown) in the barrier 619, and bypass space750.

FIG. 16 illustrates a filtration module 401 where the pump 404 is notdirectly attached to the filtration module, but which nevertheless ,generates alternating flow as previously described; the alternating flowis transferred from pump into the filtration module through conduit 461,entering the filtration module filtrate chamber 410 through the filtratechamber entrance 478. The flow dynamics through the filtration moduleremain otherwise similar to that shown in FIGS. 11 a and 11 b. Thenumbering and meaning of parts in FIG. 16 remain essentially the same asthose in FIGS. 11 a and 11 b. The separation of the pump from the moduleoffers some benefits, including simplified scale up capability and thepotential for greater pump flow control capability.

What is claimed is:
 1. A screen filter module enhanced with an externalbarrier, the module comprising: a) a retentate chamber, said chambercomprising a chamber wall and a chamber entrance, said chamber entrancepermitting fluid containing suspended particulate matter to enter orexit the chamber, and wherein the chamber wall comprises a filterscreen, said screen comprising pores, such that said screen permitsfluid and particles smaller than the pores but not suspended particulatematter larger than the pores to flow through it; b) a barrier, saidbarrier positioned exterior to the retentate chamber so as to redirectfluid moving through the filter screen area proximal to the chamberentrance so that the redirected fluid moves towards a filter screen areamore distal to the chamber entrance; c) an exiting space between thefilter screen and the barrier, said space for permitting fluid flow; d)an opening between the filter screen and the perimeter of the barrier,said opening providing a means for fluid to leave the exiting space andescape the module; and e) an upper adapter for attachment to the filterscreen, said adapter also attached to a rigid portion of the screenfilter module, so as to prevent collapse of the filter screen.
 2. Ascreen filter module enhanced with an internal barrier, the modulecomprising: a) a filtrate chamber, said chamber comprising a chamberwall and a chamber entrance, said chamber entrance permitting fluid toexit or enter the chamber, and wherein the chamber wall comprises afilter screen, said screen comprising pores, such that said screenpermits fluid and particles smaller than the pores but not suspendedparticulate matter that is larger than the pores, to flow through it; b)a barrier, said barrier positioned inside the filtrate chamber so as toredirect filtrate chamber fluid moving towards a filter screen areadistal to the filtrate chamber entrance so that the redirected fluidmoves within the filtrate chamber towards a filter screen area moreproximal to the filtrate chamber entrance and exits the filtrate chamberso as to flow into the retentate chamber; c) an opening in said barrierto allow limited fluid flow through the barrier; d) a bypass spacebetween said barrier and the filtrate chamber wall, said space forpermitting fluid entering the filtrate chamber through the filter screento bypass the barrier and flow to the filtrate chamber exit; and e) alower adapter attached to the filter screen.
 3. A compartmentalizedfiltration module that contains a screen module enhanced with anexternal barrier such that the screen filter module comprises aretentate chamber, the filtration module comprising: a) a retentatechamber, said retentate chamber comprising a retentate chamber wall anda retentate chamber entrance, said entrance permitting fluid containingsuspended particulate matter to enter and exit the chamber, saidretentate chamber wall comprising a filter screen, said screencomprising pores, such that said that said screen permits fluid andparticles smaller than said pores but not suspended particulate matterlarger than the pores to flow through it; b) a filtrate chamberadjoining said retentate chamber, said filtrate chamber comprising afiltrate chamber wall and a filtrate chamber entrance, said filtratechamber wall comprising the filter screen also comprised by theretentate chamber wall, said filtrate chamber entrance permitting fluidto enter or exit the filtrate chamber; c) an alternating pump connectedto the filtrate chamber entrance, said pump for pumping fluid inalternating directions through the filtrate chamber entrance and therebyfor pumping fluid in alternating directions through the filter screen;d) a barrier, said barrier positioned inside the filtrate chamber so asto redirect fluid moving through the filter screen area proximal to theretentate chamber entrance so that the redirected fluid moves towards afilter screen area more distal to the retentate chamber entrance; e) anexiting space between the filter screen and the barrier, said space forpermitting fluid flow; f) an opening between the filter screen and theperimeter of the barrier, said opening providing a means for fluid toescape the exiting space and the retentate chamber; g) an upper adapterfor attachment to the filter screen said adapter also attached to arigid portion of the screen filter module, so as to prevent collapse ofthe filter screen; and h) a harvest port for removing fluid from thefiltrate chamber.
 4. A compartmentalized filtration module that containsa screen filter module enhanced with an internal barrier such that thescreen filter module functions as the filtrate chamber, the filtrationmodule comprising: a) a retentate chamber, said retentate chambercomprising a retentate chamber wall and a retentate chamber entrance,said entrance permitting fluid containing suspended particulate matterto enter and exit the chamber, said retentate chamber wall comprising afilter screen, said screen comprising pores such that said screenpermits fluid and particles smaller than said pores but not suspendedparticulate matter larger than said pores to flow through it; b) afiltrate chamber adjoining said retentate chamber, said filtrate chambercomprising a filtrate chamber wall and a filtrate chamber entrance, saidfiltrate chamber wall comprising the filter screen also comprised by theretentate chamber wall, said filtrate chamber entrance permitting fluidto enter or exit the filtrate chamber; c) an alternating pump connectedto the filtrate chamber entrance, said pump for pumping fluid inalternating directions through the filtrate chamber entrance and therebyfor pumping fluid in alternating directions through the filter screen;d) a barrier, said barrier positioned inside the filtrate chamber forredirecting fluid moving towards a filter screen area distal to thefiltrate chamber entrance so that said redirected fluid moves throughthe filter screen area more proximal to the filtrate chamber entrance;e) a bypass space between said barrier and the filtrate chamber wall,said space for permitting fluid entering the filtrate chamber throughthe filter screen to bypass the barrier and flow to the filtrate chamberentrance; f) an opening in said barrier to allow limited fluid flowthrough the barrier; g) a lower adapter for attachment to the filterscreen, said adapter also attached to a rigid portion of the filtrationmodule, so as to prevent movement of the filter screen; and h) a harvestport connected to said alternating pump, said port for removing fluidpumped from the filtrate chamber.
 5. A process for removing particulatematter from a fluid in which it is suspended, the process being anexample of one that utilizes the screen filter module enhanced with anexternal barrier, the process comprising the steps of: a) feeding asuspension into a retentate chamber via an entrance in that chamber,said entrance being the retentate chamber entrance, said suspensioncomprising the particulate matter suspended in the fluid, said retentatechamber connected to a filtrate chamber via a shared filter screen intheir respective walls, said filter screen comprising pores of a sizethat allow the fluid and particles smaller than the screen pores but notthe suspended particulate matter that are larger than the screen poresto pass through, said filtrate chamber comprising an entrance connectedto an alternating pump; b) directing the suspension at the filter screenso that fluid but not said suspended particulate matter passes throughthe filter screen, said directing achieved by the action of thealternating pump; c) collecting, in the filtrate chamber, the fluid thatpassed through the screen filter, said collected fluid being thefiltrate fluid; d) removing a portion of the filtrate fluid from thefiltrate chamber, thereby leaving unremoved filtrate fluid in thefiltrate chamber; e) directing the unremoved filtrate fluid back at thescreen filter, such filter screen directing achieved by the alternatingpump exerting a force on said unremoved filtrate fluid, such that abarrier redirects filtrate fluid moving towards a filter screen areaproximal to the retentate chamber entrance so that the redirected fluidmoves towards a screen filter area more distal to the retentate chamberentrance; and f) repeating steps (a) through (e).
 6. A process forremoving particulate matter from a fluid in which it is suspended, theprocess being an example of one that utilizes the screen filter moduleenhanced with an internal barrier, the process comprising the steps of:a) feeding a suspension into a retentate chamber via an entrance in thatchamber, said entrance being the retentate chamber entrance, saidsuspension comprising the particulate matter suspended in the fluid,said retentate chamber connected to a filtrate chamber via a sharedfilter screen in their respective walls, said filter screen comprisingpores, said pores of a size that allow the fluid and particles smallerthan the pores but not the suspended particulate matter that are largerthan the screen pores to pass through, said filtrate chamber comprisingan entrance connected to an alternating pump; b) directing thesuspension at the screen so that fluid but not said suspendedparticulate matter passes through the filter screen, said directingachieved by the action of the alternating pump; c) collecting, in thefiltrate chamber, the fluid that passed through the filter screen, saidcollected fluid being the filtrate fluid; d) removing a portion of thefiltrate fluid from the filtrate chamber, thereby leaving unremovedfiltrate fluid in the filtrate chamber; e) directing the unremovedfiltrate fluid back at the screen filter, such directing achieved by thealternating pump exerting a force on said unremoved filtrate fluid, suchthat a barrier redirects fluid moving towards a screen filter areadistal to the filtrate chamber entrance so that the redirected fluidmoves towards a screen filter area more proximal to the filtrate chamberexit; and f) Repeating steps (a) through (e).